Heavy duty clutches, generally, and specifically those of the two-plate configuration, are subject to tumbling and torsional activity of their parts at idle speed and torsional activity at higher speeds when the clutch is released. In such arrangements the intermediate plate of the two-plate clutch or the pressure plate of a single-plate clutch has a tendency to tumble at slow speed and a tendency to clatter or vibrate back and forth at high speed as the edges of its drive lugs abut against the opposite edges of the drive lug slots. The first of these motions (tumbling) is caused by gravity. In this movement the lug slots on the intermediate or pressure plate seek support from horizontally opposed pairs of driving lugs, which pair of lugs constantly change relative position during rotation of the cover, imparting a tumbling motion to the intermediate or pressure plate. The second of these motions is caused by a torque loading being imposed on the intermediate plate through a non-uniform rotation of the engine, flywheel, and cover. At the same time the intermediate or pressure plate is attempting, due to inertia, to rotate uniformly. The rotational differences between the intermediate plate and the fly wheel create a torque loading on the intermediate plate. The torque loading can produce a vibratory motion in the intermediate plate that can cause the clutch to clatter.
The unwanted tumbling and vibratory motion cause a "clunking" type noise in the clutch and, additionally, subject the clutch parts to undue wear. Although wearing can be provided for fairly satisfactorily by use of strengthened structural members, recent developments in the engine field have increased the torsional vibration, causing increased wear on the driving slots. Reduction of the torsionally induced clatter reduces the wear on the driving lugs and slots.
Although various arrangements for the suppression of tumbling vibrations and rattling of clutch plates and clutch assemblies have been developed and are known to exist in the prior art, none of the known arrangements provide an extremely simple assembly which requires the use of no special mounting means and, therefore, is capable of utilizing standard clutch parts. Accordingly, it would be desirable to provide a clutch useable with the new engines that has a simply mounted vibration suppression unit to reduce the noise generated by the operation of the clutch.
In this type of heavy duty clutch the intermediate plate moves axially during the operation of the clutch, and the resulting wear. The intermediate plate is also drivingly connected to the flywheel by drive pins that engage slots in the intermediate plate. It is very important that the drive pins be properly aligned with the slots in the intermediate plate to prevent binding during the axial movement of the intermediate plate. If the drive pins and slots are not properly aligned, the intermediate plate can be restricted in axial movement. If the intermediate plate is not free to move axially, an incomplete release of the clutch and/or erratic engagement of the clutch can result.